1. Field of the Invention
This invention relates to wireless alarm systems for banks, police officers and other institutions and personnel requiring security alarm systems that cannot be detected or interferred with by law breakers.
2. Prior Art
Institutions such as banks, museums, stores and the like that are attractive or vulnerable to the activities of armed robbers, burglars, and other unlawful intruders frequently have alarm systems installed that alert private or public security personnel when the alarm system is activated. The alarm system may be of the automatic type that is activated, for example, when a locked door or window is opened or the beam of an electric eye is interrupted or a strange object (i.e., an intruder) in the space being protected is detected by reflected radio or sound waves. Or, it may be of the manual type that is activated by a person who sees or senses the presence of an unlawful intruder in the space being protected. A familiar example of this type of alarm system is the so called "silent alarm button" with which many bank teller's cages are equipped. All of these known alarm systems share in common several important disadvantages. They are all immobile or fixed in place and therefore of limited effectiveness. That is to say, the alarm system is activated only if a particular door or window is opened, or if a fixed beam of light is interrupted, or if an alarm button is within convenient reach of a teller or other person when needed. Moreover, they are all subject to being disabled by an intruder who first cuts or shuts off either the electric power supply for these alarm systems or the electric cable that transmits the alarm signal to the remote headquarters of the security personnel. In addition, an armed intruder may intimidate the teller or other person and thereby prevent the sounding of the alarm even when an alarm button is within reach of the person.
In order to overcome the aforementioned disadvantages of conventional alarm systems it has heretofore been proposed that certain employees of the institution (for example, guards, tellers, and the like) be provided with portable radio transmitters which, when activated by the person carrying the transmitter, transmits a radio or wireless alarm signal to a remote radio receiver which in turn, transmits the alarm signal by fixed or "hard" wiring to the site of the security personnel who are to be alerted. These known wireless alarm systems also have certain disadvantages which limit their usefulness. Most require the person carrying the portable transmitter to press a button or turn on a switch in order to activate the radio and transmit the wireless alarm signal. Such an act is usually quite noticeable and would be dangerous if not impossible to carry out in the presence of an armed robber. In addition, the person carrying the portable alarm may inadvertently press the transmitter button and thereby activate the alarm system with a false alarm. To provide for this possibility one such wireless alarm system has a time delay device incorporated in the radio receiver which delays for a predetermined period of time the transmittal of the alarm signal to the security personnel. In this system the person sending the false alarm has an opportunity to shut off the radio receiver before the alarm signal is automatically transmitted to the remote security personnel at the end of the predetermined period of time. However, this requires that the radio receiver be conveniently located where it can be reached within the predetermined time delay period, and this in turn, renders the system vulnerable to sabotage by intruders.
After an intensive investigation of the problems inherent in existing alarm systems, and in particular wireless alarm systems, I have now devised an improved wireless alarm system that enables a person wearing a portable wireless transmitter to activate the transmitter without any noticeable movement on the wearer's part, thereby activating the system despite the intimidating presence of armed intruders. The wireless transmitter assembly of my new alarm system includes a concealed pressure actuated switch for initiating the alarm sequence, an alarm alerting means for alerting the person wearing the transmitter assembly that the alarm sequence has been initiated and timer means for delaying the transmission of the alarm signal for a predetermined period of time, thereby virtually eliminating the problem of inadvertent false alarms. The radio transmitter transmits a coded alarm signal that is received by a remote radio receiver, thereby preventing accidental or intentional interference with the alarm sequence by uncoded wireless signals. The radio receiver is advantageously provided with its own independent power supply, and the alarm signal is advantageously relayed to the security personnel by a second radio transmitter so as to provide protection against sabotage. The alarm system is compatible with existing alarm systems and has other advantages which are hereinafter more fully explained.